I think that your question need to be clarified a bit. I assume that by ATP 1000 you mean the ATP World Tour Masters 1000 tournaments. So are you asking whether some of the tournaments has the rule that the deciding set (i.e., the 3rd set) cannot end with a tiebreak, similarly as in Grand Slams (with the exception of the US Open)?
– MartinMay 15 '16 at 9:31

1 Answer
1

According to the ATP Official Rulebook, all the ATP 1000 matches have a tie-break in the final set, even the finals:

ATP World
Tour tournaments and the ATP Challenger Tour tournaments are governed by the
ATP. Unless otherwise specified, all regulations are applicable to both ATP World
Tour and ATP Challenger Tour tournaments.
ATP World Tour tournaments
Barclays ATP World Tour Finals (singles & doubles)ATP World Tour Masters 1000
ATP World Tour 500
ATP World Tour 250
...
...
B.Matches – Number of Sets.
1) Singles. All matches, including finals, shall be the best of three (3) tie-break sets

As for why, I assume they use tie-breaks in all of these non-slam tournaments for the same reason they don't play 5 sets: so that the whole tournament is less taxing on the players (this can happen without tie-breaks). They used to play 5 sets in the finals for the masters tournaments and stopped doing that because it would wear down players enough to where they wouldn't be able to consistently play all of the masters tournaments. To give an example, in 2006, Federer and Nadal both had to pull out of Hamburg after their long 5 set final in Rome. The next year, Masters 1000's were all reduced to 3 sets, which was possibly spurred by this incident. (Even back in 2006 though, all 5 sets were tie-break sets)